The present invention relates generally to hardmetals and, more particularly, to a body having multiple-regions including at least one hardmetal body.
Hardmetal is a term used to describe a monolithic material composed of a hard particulate bond with a binder. The hard particulate comprises a nonmetallic compound or a metalloid. The hard particulate may or may not be interconnected in two or three dimensions. The binder comprises a metal or alloy and is generally interconnected in three dimensions. Each monolithic hardmetal's properties are derived from the interplay of the size distribution of the hard particulate, amount of the hard particulate, composition of the hard particulate and the composition of the binder.
A hardmetal family may be defined as a monolithic hardmetal consisting of a specified hard particulate combined with a specified binder component. Tungsten carbide bonded or cemented together by a cobalt alloy is an example of a WC-Co family and is commonly referred to as a WC-Co cemented carbide. The properties of a hardmetal family may be tailored, for example, by adjusting either separately or together an amount of the hard particulate, a size distribution of the hard particulate, or a composition of the binder. However, there is the principle that the improvement of one material property invariably decreases another. For example, in the WC-Co family as resistance to wear is improved through an increase in hard particulate amount that in turn results in the decrease of binder amount and the resistance to breakage generally decreases. A design around the principle is to combine several monolithic hardmetals to form a multiple-region hardmetal body.
The resources (i.e., both time and money) of many individuals and companies throughout the world have been directed to the development of multiple-region cemented carbide bodies. The amount of resources directed to the development effort is demonstrated by the number of publications, US and foreign patents, and foreign patent publications on the subject. Some of the many US and foreign patents, and foreign patent publications include: U.S. Pat. Nos. 2,888,247; 3,909,895; 4,194,790; 4,359,355; 4,427,098; 4,722,405; 4,743,515; 4,820,482; 4,854,405; 5,074,623; 5,333,520; and 5,335,738, and foreign patent publication nos. DE-A-3 519 101; GB-A 806 406; EPA-0 111 600; DE-A-3 005 684; DE-A-3 519 738; FR-A-2 343 885; GB-A-1 115 908; GB-A-2 017 153; and EP-A-0 542 704.
Some resources have been expended for “thought experiments” and merely present wishes—in that they fail to teach the methods of making such multiple-region cemented carbide bodies.
Other resources have been spent developing complicated methods. Some methods included the pre-engineering of starting ingredients, green body geometry or both. For example, the starting ingredients used to make a multiple-region cemented carbide body are independently formed as distinct green bodies. Sometimes, the independently formed green bodies are also independently sintered and, sometimes after grinding, assembled, for example, by soldering, brazing or shrink fitting to form a multiple-region cemented carbide body. Other times, independently formed green bodies are assembled and then sintered. The different combinations of the same ingredients that comprise the independently formed green bodies respond to sintering differently. Each combination of ingredients shrinks uniquely. Each combination of ingredients responds uniquely to a sintering temperature, time, atmosphere or any combination of the proceeding. Only the pre-engineering of forming dies and, thus, green body dimensions allows assembly followed by sintering. To allow the pre-engineering, an extensive database containing the ingredient's response to different temperatures, times, atmospheres or any combination of the proceeding is required. The building and maintaining of such databases are cost prohibitive. To avoid those costs, elaborate process control equipment might be used. This too is expensive. Further, when using elaborate process control equipment, minor deviations from prescribed processing parameters rather than yielding useful multiple-region cemented carbide bodies—yield scrap.
Still other resources have been expended on laborious methods for forming multiple-region cemented carbide bodies. For example, sub-stoichiometric monolithic cemented carbide bodies are initially sintered. Their compositions are deficient with respect to carbon and thus the cemented carbides contain eta-phase. The monolithic cemented carbide bodies are then subjected to a carburizing environment that reacts to eliminate the eta-phase from a periphery of each article. These methods, in addition to the pre-engineering of the ingredients, require intermediate processing steps and carburizing equipment. Furthermore, the resultant multiple-region cemented carbide bodies offer only minimal benefits since once the carburized peripheral region wears away, their usefulness ceases.
Some resent methods include those discussed in U.S. Pat. Nos. 5,541,006; 5,697,046; 5,686,119; 5,762,843; 5,789,686; 5,792,403; 5,677,042; 5,679,445; 5,697,042; 5,776,593; and 5,806,934, all assigned to Kennametal. Although these patents teach satisfactory alternatives for making multiple-region cemented carbide bodies there is still room for improvement.
It is apparent that there is a need for multiple-region cermet bodies and cemented carbide bodies that can be inexpensively manufactured. Further, there exists a need for multiple-region cermet bodies and cemented carbide bodies that further exhibit superior wear resistance and can be inexpensively manufactured.